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partial case-on-constructor

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This commit is contained in:
Ulf Norell 2019-09-27 16:37:13 +02:00
parent 43fa667f03
commit ac9e9716cb
1 changed files with 41 additions and 11 deletions
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52
src/aeso_ast_to_fcode.erl
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@ -1333,7 +1333,7 @@ simplify(Env, {proj, {var, X}, I} = Expr) ->
end;
simplify(Env, {switch, Split}) ->
case simpl_switch(Env, Split) of
case simpl_switch(Env, [], Split) of
nomatch -> {builtin, abort, [{lit, {string, <<"Incomplete patterns">>}}]};
stuck -> {switch, Split};
Expr -> Expr
@ -1357,21 +1357,51 @@ simpl_proj(Env, I, Expr) ->
_ -> false
end.
simpl_switch(_Env, {nosplit, E}) -> E;
simpl_switch(Env, {split, _, X, Alts}) ->
case constructor_form(Env, {var, X}) of
false -> stuck;
E -> simpl_switch(Env, E, Alts)
get_catchalls(Alts) ->
[ C || C = {'case', {var, _}, _} <- Alts ].
%% The scode compiler can't handle multiple catch-alls, so we need to nest them
%% inside each other. Instead of
%% _ => switch(x) ..
%% _ => e
%% we do
%% _ => switch(x)
%% ..
%% _ => e
add_catchalls(Alts, []) -> Alts;
add_catchalls(Alts, Catchalls) ->
case lists:splitwith(fun({'case', {var, _}, _}) -> false; (_) -> true end,
Alts) of
{Alts1, [C]} -> Alts1 ++ [nest_catchalls([C | Catchalls])];
{_, []} -> Alts ++ [nest_catchalls(Catchalls)]
%% NOTE: relies on catchalls always being at the end
end.
simpl_switch(_, _, []) -> nomatch;
simpl_switch(Env, E, [{'case', Pat, Body} | Alts]) ->
nest_catchalls([C = {'case', {var, _}, {nosplit, _}} | _]) -> C;
nest_catchalls([{'case', P = {var, _}, {split, Type, X, Alts}} | Catchalls]) ->
{'case', P, {split, Type, X, add_catchalls(Alts, Catchalls)}}.
simpl_switch(_Env, _, {nosplit, E}) -> E;
simpl_switch(Env, Catchalls, {split, Type, X, Alts}) ->
Alts1 = add_catchalls(Alts, Catchalls),
Stuck = {switch, {split, Type, X, Alts1}},
case constructor_form(Env, {var, X}) of
false -> Stuck;
E ->
case simpl_case(Env, E, Alts1) of
stuck -> Stuck;
Res -> Res
end
end.
simpl_case(_, _, []) -> nomatch;
simpl_case(Env, E, [{'case', Pat, Body} | Alts]) ->
case match_pat(Pat, E) of
false -> simpl_switch(Env, E, Alts);
false -> simpl_case(Env, E, Alts);
Binds ->
Env1 = maps:merge(Env, maps:from_list(Binds)),
case simpl_switch(Env1, Body) of
nomatch -> simpl_switch(Env, E, Alts);
case simpl_switch(Env1, get_catchalls(Alts), Body) of
nomatch -> simpl_case(Env, E, Alts);
stuck -> stuck;
Body1 -> let_bind(Binds, Body1)
end